// 函数

// 背景图片
bg-image($url)
  background-image url($url + '@2x.png')
  @media (-webkit-min-device-pixel-ratio: 3), (min-device-pixel-ratio: 3)
    background-image url($url + '@3x.png')
// 不换行
no-wrap()
  text-overflow ellipsis
  overflow hidden
  white-space nowrap
// 扩展点击区域
extend-click()
  position relative
  &:before
    content ''
    position absolute
    top -10px
    left -10px
    right -10px
    bottom -10px
flex-center()
  display flex
  align-items center
